Mapping and ablation method for the treatment of ventricular tachycardia

ABSTRACT

An apparatus for mapping and/or ablating tissue includes a braided conductive member that may be inverted to provide a ring-shaped surface. When a distal tip of the braided conductive member is retracted within the braided conductive member, the lack of a protrusion allows the ring-shaped surface to contact a tissue wall such as a cardiac wall. In an alternative configuration, the braided conductive member may be configured with the distal portion forming a proboscis that can be used to stably position the braided conductive member relative to a blood vessel, such as a ventricular outflow tract. The braided conductive member has a plurality of electronically active sites that may be accessed individually for stable mapping over a broad area for stable mapping or ablation to form broad and deep lesions.

RELATED APPLICATIONS

This application claims priority under 35 U.S.C. §119(e) to U.S.Provisional Application Ser. No. 60/571,781, entitled “MAPPING ANDABLATION METHOD AND APPARATUS FOR THE TREATMENT OF IDIOPATHICVENTRICULAR TACHYCARDIA ORIGINATING FROM RVOT OR LVOT,” filed on May 17,2004, which is herein incorporated by reference in its entirety, andU.S. Provisional Application Ser. No. 60/571,843, entitled “MAPPING ANDABLATION METHOD AND APPARATUS FOR THE TREATMENT OF IDIOPATHICVENTRICULAR TACHYCARDIA,” filed on May 17, 2004, which is hereinincorporated by reference in its entirety. This application claimspriority under 35 U.S.C. §119(e) to U.S. Provisional Application Ser.No. 60/571,821, entitled “METHOD AND APPARATUS FOR MAPPING AND/ORABLATION OF CARDIAC TISSUE,” filed on May 17, 2004, which is hereinincorporated by reference in its entirety.

BACKGROUND OF INVENTION

1. Field of Invention

The invention relates generally to medical devices for performingmapping and ablation procedures. More particularly, the inventionrelates to a system for mapping and/or ablating cardiac walls.

2. Discussion of Related Art

The human heart is a very complex organ, which relies on both musclecontraction and electrical impulses to function properly. The electricalimpulses travel through the heart walls, first through the atria andthen the ventricles, causing the corresponding muscle tissue in theatria and ventricles to contract. Thus, the atria contract first,followed by the ventricles. This order is essential for properfunctioning of the heart.

Over time, the electrical impulses traveling through the heart can beginto travel in improper directions, thereby causing the heart chambers tocontract at improper times. Such a condition is generally termed acardiac arrhythmia, and can take many different forms. When the chamberscontract at improper times, the amount of blood pumped by the heartdecreases, which can result in premature death of the person.

Techniques have been developed which are used to locate cardiac regionsresponsible for the cardiac arrhythmia, and also to disable theshort-circuit function of these areas. According to these techniques,electrical energy is applied to a portion of the heart tissue to ablatethat tissue and produce scars which interrupt the reentrant conductionpathways or terminate the focal initiation. The regions to be ablatedare usually first determined by endocardial mapping techniques. Mappingmay be active or passive. Active mapping, sometimes called “pacemapping,” typically involves percutaneously introducing a catheterhaving one or more electrodes into the patient, passing the catheterthrough a blood vessel (e.g. the femoral vein or artery) and into anendocardial site (e.g., the atrium or ventricle of the heart), anddeliberately inducing an arrhythmia so that a continuous, simultaneousrecording can be made with a multichannel recorder at each of severaldifferent endocardial positions. Passive mapping techniques typicallyinvolve sensing electrical signals from the electrodes on the catheter.

When an arrythromogenic focus or inappropriate circuit is located, asindicated in the electrocardiogram recording, it is marked by variousimaging or localization means so that cardiac arrhythmias emanating fromthat region can be blocked by ablating tissue. An ablation catheter withone or more electrodes can then transmit electrical energy to the tissueadjacent the electrode to create a lesion in the tissue. One or moresuitably positioned lesions will typically create a region of necrotictissue which serves to disable the propagation of the errant impulsecaused by the arrythromogenic focus. Ablation is carried out by applyingenergy to the catheter electrodes. The ablation energy can be, forexample, RF, DC, ultrasound, microwave, or laser radiation.

Atrial fibrillation together with atrial flutter are the most commonsustained arrhythmias found in clinical practice. Current understandingis that atrial fibrillation is frequently initiated by a focal triggerfrom the orifice of or within one of the pulmonary veins. Though mappingand ablation of these triggers appears to be curative in patients withparoxysmal atrial fibrillation, there are a number of limitations toablating focal triggers via mapping and ablating the earliest site ofactivation with a “point” radiofrequency lesion. One way to circumventthese limitations is to determine precisely the point of earliestactivation. Once the point of earliest activation is identified, alesion can be generated to electrically isolate the trigger with alesion; firing from within those veins would then be eliminated orunable to reach the body of the atrium, and thus could not triggeratrial fibrillation.

Another method to treat focal arrhythmias is to create a continuous,annular lesion around the ostia (i.e., the openings) of either the veinsor the arteries leading to or from the atria, thus “corralling” thesignals emanating from any points distal to the annular lesion.Conventional techniques include applying multiple point sources aroundthe ostia in an effort to create such a continuous lesion. Such atechnique is relatively involved, and requires significant skill andattention from the clinician performing the procedures.

Another source of arrhythmias may be from reentrant circuits in themyocardium itself. Such circuits may not necessarily be associated withvessel ostia, but may be interrupted by means of ablating tissue eitherwithin the circuit or circumscribing the region of the circuit. Itshould be noted that a complete “fence” around a circuit or tissueregion is not always required in order to block the propagation of thearrhythmia; in many cases simply increasing the propagation path lengthfor a signal may be sufficient. Conventional means for establishing suchlesion “fences” include a multiplicity of point-by-point lesions,dragging a single electrode across tissue while delivering energy, orcreating an enormous lesion intended to inactivate a substantive volumeof myocardial tissue.

U.S. Pat. No. 6,315,778 B1, entitled “Apparatus For Creating AContinuous Annular Lesion,” which is herein incorporated by reference,discloses a medical device which is capable of ablating a ring of tissuearound the ostia of either veins or arteries leading to or from theatria. The medical device includes a protrusion that inserts into anostium, thereby allowing electrodes to contact tissue near the ostium.

In some instances, it is desirable to perform mapping and/or ablationprocedures on a cardiac wall (or other tissue) that is not located nearan ostium. In such a scenario, the lack of a protrusion may help toallow electrodes of a device contact the cardiac wall or other tissue.In other cases, mapping and/or ablation may be desired at severallocations around an ostium and it would be helpful to be able toposition electrodes without concern for a protrusion that may hindercontact between electrodes and the cardiac wall.

Another type of arrhythmia is Ventricular tachycardia. Ventriculartachycardia (VT) usually arises in diseased myocardium. However, VT canoccur in the absence of structural heart disease, or at least in heartsin which current diagnostic techniques fail to identify any anatomic orfunctional abnormalities. These arrhythmias have been termed “idiopathicVTs”. The mechanisms underlying idiopathic VT are varied and includereentry and triggered activity due to delayed after depolarizations.

Idiopathic VTs that arise from the right or left ventricular outflowtract (RVOT VT and LVOT VT) have been reported. Thus RVOT VT and LVOT VTpatients could be treated with RF ablation. However, the success rate ofablation therapy for treatment of VT is affected by many factors, suchas the inability to induce tachycardia to permit mapping, and thepresence of deep, often septal sites of origin that are resistant to RFablation with conventional ablation catheters, usually a 4-mm ablationcatheter. Treating VT in the area of the outflow track with ablationtherapy has been difficult.

SUMMARY OF INVENTION

Embodiments of the present invention encompass apparatus and methods formapping electrical activity within the heart. Embodiments of the presentinvention also encompass methods and apparatus for creating lesions inthe heart tissue (ablating) to create a region of necrotic tissue whichserves to disable the propagation of errant electrical impulses causedby an arrhythmia. The apparatus and methods described herein also may beused for mapping and ablating of tissue other than heart tissue.

In one aspect, the invention relates to a method of treating anarrhythmia in a heart, comprising the acts of: introducing a substrateinto a chamber of the heart; placing the substrate in contact with theheart while in a first configuration; (c) performing mapping and/orpacing by transmitting electrical signals between the substrate and acontrol location; reconfiguring the substrate into a secondconfiguration, different than the first configuration; and ablating aregion of the heart adjacent the substrate.

In another aspect, the invention relates to a method of detecting afocus of an arrhythmia in a heart, comprising the acts of introducinginto a chamber of the heart a substrate having a plurality ofelectrically active sites thereon, the substrate configured to have adistally facing surface with a first area; reconfiguring the substrateto expand the distally facing surface to have a second area, larger thanthe first area; contacting the distally facing surface with the heart ina region having the second surface area; using the electrically activesites to detect at least one focus of the arrhythmia over the region ofthe heart; and ablating a sub-region of the region selected in responseto the detection of a focus within the region.

In a further aspect, the invention relates to a method of detecting afocus of an arrhythmia in a heart, comprising the acts of introducing acatheter having a substrate into a chamber of the heart; configuring thesubstrate to provide a surface; positioning the catheter so that aplurality of electrically active sites on the surface are in electricalcontact with the endocardium; and using signals transmitted between acontrol location and the plurality of electrically active sites todetect a focus.

In yet a further aspect, the invention relates to A method of treatingan arrhythmia in a heart, comprising the acts of introducing a catheterhaving a plurality of electrically active sites into the heart; with thecatheter, sensing electrical signals produced by the heart; with thecatheter, providing electrical stimulus to the heart; and with thecatheter, ablating a region of the heart.

In a further aspect, the invention relates to A method of treatingventricular tachycardia in a heart, comprising the acts of positioning asurface of a catheter against a surface of the heart adjacent the ostiumof an outflow tract of a ventricle of the heart, the surface of thecatheter having a periphery substantially the same as or greater than aperiphery of the ostium; using the catheter to detect a position of atleast one focus of the ventricular tachycardia; and selectively ablatinga portion of the heart based on the position of the at least one focus.

BRIEF DESCRIPTION OF DRAWINGS

The accompanying drawings are not intended to be drawn to scale. In thedrawings, like components that are illustrated in various figures arerepresented by a like numeral. For purposes of clarity, not everycomponent may be labeled in every drawing. In the drawings:

FIG. 1 illustrates an overview of a mapping and ablation catheter systemthat may be used in one embodiment of the present invention;

FIG. 2 illustrates a braided conductive member in an undeployed statethat may be used in one embodiment of the invention;

FIG. 3 illustrates a braided conductive member in a partially expandedstate that may be used in one embodiment of the invention;

FIG. 4 illustrates a braided conductive member in an inverted state thatmay be used in one embodiment of the invention;

FIG. 5 illustrates a braided conductive member in an inverted statewhere a distal end of the braided conductive member does not protrudedistally from the inverted braided conductive member that may be used inone embodiment of the invention;

FIG. 6 illustrates a braided conductive member including supportelements that may be used in one embodiment of the invention;

FIG. 7 illustrates a braided conductive member that may be used in oneembodiment of the invention;

FIG. 8 illustrates an alternate embodiment of the braided conductivemember that may be used on one embodiment of the invention;

FIG. 9 illustrates the use of irrigation according to one embodiment ofthe invention;

FIG. 10 illustrates the use of irrigation according to anotherembodiment of the invention;

FIG. 10A is an enlarged cross-sectional view of a filament used in thebraided conductive member illustrated in FIG. 10;

FIG. 11 illustrates one embodiment of a method of using a catheter andthe braided conductive member;

FIG. 12 is a sketch illustrating electrically active sites on a surfaceof a catheter;

FIG. 13 is a sketch illustrating a method of treating arrhythmia;

FIG. 14A is a sketch illustrating a method of treating arrhythmia;

FIG. 14B is a sketch illustrating a pattern of lesions formed inaccordance with the method of FIG. 14A;

FIG. 14C is a sketch illustrating an alternative pattern of lesionsformed in accordance with the method of FIG. 14A; and

FIG. 14D is a sketch illustrating an alternative pattern of lesionsformed in accordance with the method of FIG. 14A.

DETAILED DESCRIPTION

This invention is not limited in its application to the details ofconstruction and the arrangement of components and acts set forth in thefollowing description or illustrated in the drawings. The invention iscapable of other embodiments and of being practiced or of being carriedout in various ways. Also, the phraseology and terminology used hereinis for the purpose of description and should not be regarded aslimiting. The use of “including,” “comprising,” or “having,”“containing”, “involving”, and variations thereof herein, is meant toencompass the items listed thereafter and equivalents thereof as well asadditional items.

System Overview

Reference is now made to FIG. 1, which illustrates an overview of aelectrophysiology system, such as may be used for mapping and/orablation to detect or treat cardiac arrhythmia. The system includes acatheter 10 having a shaft portion 12, a control handle 14, a connectorportion 16, and a braided conductive member 28. A controller 8 isconnected to connector portion 16 via cable 6. Ablation energy generator4 may be connected to controller 8 via cable 3. A recording device 2 maybe connected to controller 8 via cable 1. When used in an ablationapplication, controller 8 is used to control ablation energy provided tocatheter 10 by ablation energy generator 4. When used in a mappingapplication, controller 8 is used to process signals coming fromcatheter 10 and to provide these signals to recording device 2. Althoughillustrated as separate devices, recording device 2, ablation energygenerator 4, and controller 8 could be incorporated into a single deviceor two devices.

In this description, various aspects and features of exemplaryembodiments of the present invention will be described. These aspectsand features are discussed separately for clarity. One skilled in theart will appreciate that the features may be selectively combined in adevice depending upon the particular application. Furthermore, any ofthe various features may be incorporated in a catheter and associatedmethod of use for either mapping and/or ablation procedures.

Catheter Overview

Reference is now made to FIGS. 2-5, which illustrate a catheter that maybe used in the electrophysiology system of FIG. 1. Embodiments of thepresent invention generally include a catheter and methods of its usefor mapping and ablation in electrophysiology procedures. FIG. 2illustrates braided conductive member 28 in an unexpanded state. In thisembodiment, the unexpanded state of the braided conductive member is anundeployed configuration. Braided conductive member 28 is, in oneembodiment of the invention, a plurality of interlaced, electricallyconductive filaments 34 which are attached at a distal end 18 with a cap24 and also at a proximal end 19 with an anchoring element 32. Of courseany suitable element or method may be used to attach or anchor filaments34.

FIG. 3 illustrates braided conductive member 28 in a partially expandedstate. Each of FIGS. 2 and 3 show a state in which braided conductivemember 28 is completely everted. FIG. 4 illustrates braided conductivemember 28 in a first deployed configuration option which may be used tolocate braided conductive member 28 at an ostium.

In FIG. 4, distal end 18 of braided conductive member 28 is partiallyinverted. The terms “partially invert” and “partially inverted”, forpurposes herein, refer to a configuration in which portions of filamentsare retracted within the braided conductive member such that they are atleast partially surrounded by other portions of filaments. A tip, orother portions of the braided conductive member may protrude distallyfrom any distally-facing surface of the braided conductive member whenthe braided conductive member is partially inverted.

FIG. 5 illustrates braided conductive member 28 in a second deployedconfiguration option which may be used to effect contact between anannular surface of braided conductive member 28 and a cardiac wall (see,for example, FIG. 11) other cardiac tissue, or other target tissue. InFIG. 5, the distal tip of braided conductive member 28 is inverted. Theterms “invert” or “inverted”, for purposes herein, refer to aconfiguration in which the distal tip or distal end of the braidedconductive member is retracted such that the distal tip does notprotrude distally from a distally-facing surface of the braidedconductive member. For purposes herein, the terms “evert” or “everted”refer to a configuration in which the distal tip or distal end of thebraided conductive member protrudes distally from any distally-facingannular surface that is present. An everted configuration does not,however, require that a distally-facing annular surface be present. Insome embodiments, such as the embodiment illustrated in FIG. 2, thebraided conductive member is fully elongated in an evertedconfiguration. The term “completely everted”, when referring to a distalregion of a braided conductive member, refers to a configuration inwhich no portion of the distal region of the braided conductive memberis inverted within itself.

A braided conductive member adjustment element, such as a cable 22, isattached to distal end 18 of braided conductive member 28. Cable 22 mayextend through a lumen (not shown) in shaft portion 12 and through theinterior of braided conductive member 28. Cable 22 may be attached todistal end 18 of braided conductive member 28 using cap 24, an anchorband, or any suitable attachments or anchoring element or method knownin the art. At the control handle end, cable 22 may be attached to acontrol element, such as a slide actuator for example, that allows auser to retract and advance cable 22. It should be noted that cable 22is a separate element from cables 1, 3 and 6. Of course, braidedconductive member adjustment element need not be a cable as any suitableelement for adjusting the braided conductive member may be used. Forexample, a sheath may be used to push the braided conductive member overthe distal tip of the braided conductive member to invert braidedconductive member 28.

In operation, moving cable 22 in the proximal direction causes braidedconductive member 28 to compress longitudinally and/or to expandradially, as shown in FIG. 3. Further proximal movement of cable 22causes a portion of braided conductive member 28 to invert as shown inFIG. 4. Even further proximal movement of cable 22 may retract distalend 18 such that distal end 18 is encircled by a portion of braidedconductive member 28. In some embodiments, distal end 18 may besurrounded or partially surrounded by a portion of braided conductivemember 28 that does not form a circle.

In some embodiments, a certain amount of movement of cable 22 in theproximal direction may occur without user actuation due to the bias ofthe braided conductive member 28. For example, braided conductive member28 may be longitudinally extended beyond a relaxed state by radiallycompressing braided conductive member 28 with a sheath 33 (see FIG. 2).Upon retraction of sheath 33, braided conductive member 28 may radiallyexpand a certain amount due to its filament winding structure, or due toelastic or spring elements attached to the filaments. In furtherembodiments, cable 22 may be used to urge braided conductive member 28back into a longitudinally extended state by pushing on cap 24 or otherdistal attachment portion.

By retracting distal end 18 of braided conductive member 28 at least acertain distance in the proximal direction, a braided conductive memberannular surface 30 may be formed in a plane that is substantiallyperpendicular to a distal end 26 of shaft portion 12, as illustrated inFIG. 4. Retracting distal end 18 further removes the projection ofdistal end 18 beyond annular surface 30, as illustrated in FIG. 5, whichmay allow annular surface 30 to be placed in contact with a cardiac wallor other cardiac tissue. If braided conductive member 28 is onlypartially inverted and distal end 18 projects beyond annular surface 30in the distal direction, it may hinder efforts to contact cardiac tissuewith the annular surface. In some embodiments, however, it may bedesirable to maintain a portion of distal end 18 projecting from braidedconductive member 28 so that braided conductive member 28 may bepositioned relative to an ostium by inserting distal end 18 into theostium. In some embodiments, the annular surface may be arranged suchthat it is contactable to a substantially flat area of tissue that hasno ostia, even though an element may protrude distally from the annularsurface. For example, a highly flexible element, such as a touch sensor,may protrude distally from the inverted braided conductive member andthe annular surface would still be arranged such that it is contactableto a substantially flat area of tissue that has no ostia. The touchsensor may be a bend sensor that is positioned on the distal tip of thebraided conductive member and protrudes slightly from thedistally-facing surface when the braided conductive member is put into adeployed configuration. The bend sensor bends upon encountering a tissuewall and signals the controller that it has bent. The flexibility of thebend sensor allows the braided conductive member to contact the wall.

A “surface” need not be a continuous surface. For purposes herein, a“surface” of braided conductive member 28 refers to a plurality ofinterlaced conductive elements, such as filaments or wires, even thoughthe interlaced elements may not fully occupy the space considered to bethe surface. In some embodiments, wires or other conductive elements maybe attached to or embedded in a flexible support material such that asolid surface is present.

The annular surface formed by inverting the braided conductive member 28may have electrodes spaced around the entire annular surface. In otherembodiments, electrodes may be positioned only on a portion or portionsof the ring-shaped surface.

As illustrated in FIGS. 2-5, a sheath 33 may be provided. Sheath 33serves to protect shaft portion 12 and braided conductive member 28during manipulation through the patient's vasculature. In addition,sheath 33 may shield braided conductive member 28 from the patient'stissue in the event ablation energy is prematurely delivered to thebraided conductive member 28.

Sheath 33 may be advanced and retracted over shaft portion 12 in anysuitable manner. Control handle 14 may be used to effect the advancementor retraction of sheath 33. U.S. Pat. Nos. 5,383,852, 5,462,527, and5,611,777, which are herein incorporated by reference in theirentireties, illustrate examples of control handles that can controlsheath 33. As described in these patents, control handle 14 may includea slide actuator which is axially displaceable relative to the handle.The slide actuator may be connected to sheath 33 to retract sheath 33 toexpose braided conductive member 28 once the distal end of the catheterhas been positioned within the heart or other target location.

Braided conductive member 28 may be shaped or biased such that whensheath 33 is retracted, braided conductive member 28 expands slightly inthe radial direction. In other embodiments, braided conductive member 28may maintain its longitudinally extended shape until cable 22 or otheradjustment element is pulled in the proximal direction to longitudinallycompress braided conductive member 28. In still other embodiments,braided conductive member 28 may maintain a radial size similar to itsrelaxed state radial size when distal tip 18 is moved proximally, oreven when braided conductive member 28 is inverted.

Braided conductive member 28 is, in one embodiment of the invention, aplurality of interlaced, electrically conductive filaments 34. In someembodiments, braided conductive member 28 is a wire mesh. The filaments34 are preferably formed of metallic elements having relatively smallcross sectional diameters, such that the filaments are flexible and thebraided conductive member can be expanded radially outwardly. In oneembodiment, the filaments may be round in cross-section, having adimension on the order of about 0.001-0.030 inches in diameter.Alternatively, the filaments may have flat sides in cross-section, withthicknesses on the order of about 0.001-0.030 inches, and widths on theorder of about 0.001-0.030 inches. The filaments may be formed ofnitinol-type wire or other shape memory alloys. Alternatively, thefilaments may include non-metallic elements woven with metallicelements, with the non-metallic elements providing support to and/orseparation of the metallic elements. A multiplicity of individualfilaments 34 may be provided in braided conductive member 28, forexample three hundred or more filaments. Instead of a multiplicity orplurality of filaments, a smaller number of filaments, or even only onecontinuous filament may be arranged to form braided conductive member28. For purposes herein, the terms “filaments” or “plurality offilaments” may refer to one continuous filament that is interlaced withitself to form a braided conductive member.

Each of the filaments 34 may be electrically isolated from each other byan insulation coating. This insulation coating may be, for example, apolyamide type material. In one manner of forming an electrode, aportion of the insulation on the filaments forming an outercircumferential surface of braided conductive member 28 is removed. Thisarrangement allows each of the filaments 34 to form an isolatedelectrode, not in electrical contact with any other filament, that maybe used for mapping and ablation. In some embodiments, an electrode maycontact a coated section of another filament. Alternatively, specificelectrodes may be permitted to contact each other to form a preselectedgrouping. Methods of removing insulation from filaments 34 are disclosedin PCT Publication No. WO 02/087437, which is herein incorporated byreference in its entirety. The insulation may also be removed in apreferential manner so that a particular portion of the circumferentialsurface of a filament 34 is exposed. In this manner, when braidedconductive member 28 is radially expanded, the stripped portions offilaments may preferentially face an intended direction of mapping orablation.

Further, in some embodiments some of filaments 34 may be used formapping or electrical measurement, while others of filaments 34 may beused for ablation. The mapping and ablation filaments may be activatedindependently or may be activated concurrently. One application ofdedicating some filaments for mapping and others for ablation is using asingle braided conductive member 28 to both form a lesion and measurethe quality of the lesion. Such an arrangement can avoid a change ofcatheters during a medical procedure. Temperature sensors (not shown)also may be included on catheter shaft 12 or braided conductive member28.

A wire (not shown) may run from each of the filaments 34 to connectorportion 16 via conductors (not shown). A multiplexer or switch box maybe connected to the conductors so that each filament 34 may becontrolled individually. This function may be incorporated intocontroller 8. In some embodiments, a number of filaments 34 may begrouped together for mapping and ablation. Alternatively, eachindividual filament 34 may be used as a separate mapping channel formapping individual electrical activity at a single point. Using a switchbox or multiplexer to configure the signals being received by filaments34 or ablation energy sent to filaments 34 results in a large number ofpossible combinations of filaments for detecting electrical activityduring mapping procedures and for applying energy during an ablationprocedure.

Catheter 10 may also have a reference electrode (not shown) mounted onshaft 12 so that the reference electrode is located outside the heartduring unipolar mapping operations.

Individual control of the electrical signals received from filaments 34allows catheter 10 to be used for bipolar (differential or betweenfilament) type mapping as well as unipolar (one filament with respect toa reference electrode) type mapping.

Catheter 10 may be a steerable device, in some embodiments, in that thedistal end 26 may be deflected by an actuator contained within controlhandle 14. Control handle 14 may include a rotatable thumb wheel whichcan be used by a user to deflect distal end 26 of the catheter. Thethumb wheel (or any other suitable actuating device) is connected to oneor more pull wires (not shown) which extend through shaft portion 12 andconnect to distal end 18 of the catheter at an off-axis location,whereby tension applied to one or more of the pull wires causes thedistal portion of the catheter to curve in a predetermined direction ordirections. U.S. Pat. Nos. 5,383,852, 5,462,527, and 5,611,777illustrate various embodiments of control handle 14 that may be used forsteering catheter 10.

In some embodiments, a proximal portion of braided conductive member 28includes support elements to aid in maintaining the shape and/orstructural integrity of portions of braided conductive member 28 whendistal end 18 is moved in the proximal direction. For example, supportelements may include support filaments 34′ that are stronger, thicker ormore rigid at their proximal ends than at their distal ends, asillustrated in FIG. 6. In other embodiments, splines 35 or othernon-filament elements may be included, such as by interlacing supportelements among filaments 34, as illustrated in FIG. 7. In still furtherembodiments, support elements which are not interlaced with filaments 34may be included. In some embodiments, support elements attach to aproximal anchoring element 32 at a first end and to cap 24 or filaments34 at a second end.

Referring to FIG. 7, an embodiment of the invention having alongitudinally asymmetrically shaped braided conductive member 28 isillustrated. In this embodiment, a maximum diameter 36 of braidedconductive member 28 is located closer to distal end 18 than to proximalanchoring element 32. In one embodiment, maximum diameter 36 islongitudinally located more than two-thirds of the way from the proximalanchoring location to the distal attachment location. As cable 22 isdrawn in the proximal direction to move cap 24, splines 35 support themore proximal region of braided conductive member 28.

Reference is now made to FIG. 8 which illustrates another shape ofbraided conductive member 28. As described above regarding variousembodiments of the invention, braided conductive member 28 may begenerally radially symmetrical. However, certain anatomical structuresmay have complex three-dimensional shapes that are not easilyapproximated by a geometrically symmetrical mapping or ablationstructure. To successfully contact these types of anatomical structures,braided conductive member 28 can be “preformed” to a close approximationof that anatomy, and yet still be flexible enough to adapt to variationsfound in specific patients. Alternatively, braided conductive member 28can be of sufficient strength (as by choice of materials, configuration,etc.) to force the tissue to conform to variations found in specificpatients. For example, FIG. 8 illustrates braided conductive member 28disposed about shaft 12 in an off-center or non-concentric manner suchthat braided conductive member 28 is radially asymmetrically-shaped. Inaddition, braided conductive member 28 may also be constructed so thatthe annular surface of the braided conductive member in its expandedconfiguration is a non-circular surface so as to improve tissue contact.FIG. 8 illustrates an example of this type of configuration where thebraided conductive member 28 is constructed and arranged to benon-concentric with respect to a longitudinal axis of braided conductivemember 28 and also, in its expanded configuration, to have an asymmetricshape. In some embodiments, the asymmetric expanded configurations andthe eccentricity of braided conductive member 28 with respect to thelongitudinal axis can be produced by providing additional structuralsupports in braided conductive member 28, for example, by adding nitinolwire, ribbon wire, splines, and so on. Other suitable methods ofcreating the eccentric and/or asymmetric shape include: varying thewinding pitch; varying individual filament size and/or placement;deforming selective filaments in braided conductive member 28; and anyother suitable method known to those skilled in the art.

An asymmetrically-shaped braided conductive member may allow for theformation of a ring-shaped surface that is disposed at an angle togeneral longitudinal direction of the braided member and/or the distalend of the catheter. The angled surface may permit better contact withcertain tissue areas. In still other embodiments, inverting the braidedconductive member may form a non-planar surface. For example, differingfilament diameters may allow for the formation of a ring-shaped surfacewhich includes a section that is substantially perpendicular to thecatheter and a section that is disposed at an angle to the catheter. Theangle of the surface relative to the catheter may change continuouslyacross the surface in still other embodiments.

In some embodiments of the present invention, catheter 10 may be coatedwith a number of coatings that enhance the operating properties ofbraided conductive member 28. The coatings may be applied by any of anumber of techniques and the coatings may include a wide range ofpolymers and other materials.

Braided conductive member 28 may be coated to reduce its coefficient offriction, thus reducing the possibility of thrombi adhesion to thebraided conductive member as well as the possibility of vascular oratrial damage. These coatings can be combined with insulation (ifpresent) on the filaments that make up braided conductive member 28.These coatings may be included in the insulation itself, or the coatingsmay be applied over the insulation layer.

Braided conductive member 28 also may be coated to increase or decreaseits thermal conduction, which can improve the safety or efficacy of thebraided conductive member 28. This change in thermal conduction may beachieved by incorporating thermally conductive elements or thermallyinsulating elements into the electrical insulation of the filaments thatmake up braided conductive member 28, or by adding a coating to theassembly. Polymer mixing, IBAD, or similar technology could be used toadd Ag, Pt, Pd, Au, Ir, Cobalt, and others into the insulation or tocoat braided conductive member 28.

In some embodiments, radioopaque coatings or markers may be used toprovide a reference point for orientation of braided conductive member28 when viewed during fluoroscopic imaging. The materials that provideradiopacity include, for example, Au, Pt, Ir, and others known to thoseskilled in the art. These materials may be incorporated and used ascoatings as described above.

Antithrombogenic coatings, such as heparin and BH, can also be appliedto braided conductive member 28 to reduce thrombogenicity to preventblood aggregation on braided conductive member 28. These coatings can beapplied by dipping or spraying, for example.

As noted above, the filament 34 of braided conductive member 28 may beconstructed of metal wire materials. These materials may be, forexample, MP35N, nitinol, or stainless steel. Filaments 34 may also becomposites of these materials in combination with a core of anothermaterial such as silver or platinum. The combination of a highlyconductive electrical core material with another material forming theshell of the wire allows the mechanical properties of the shell materialto be combined with the electrical conductivity of the core material toachieve better and/or selectable performance. The choice and percentageof core material used in combination with the choice and percentage ofshell material used can be selected based on the desired performancecharacteristics and mechanical/electrical properties desired for aparticular application.

There may be times during ablation or mapping procedures when catheter10 passes through difficult or tortuous vasculature. During these times,it may be helpful to have a guiding sheath (not shown) through which topass catheter 10 so as to allow easier passage through the patient'svasculature.

Irrigation

It is known that for a given electrode side and tissue contact area, thesize of a lesion created by radiofrequency (RF) energy is a function ofthe RF power level and the exposure time. At higher powers, however, theexposure time can be limited by an increase in impedance that occurswhen the temperature at the electrode-tissue interface approaches at100° C. One way of maintaining the temperature less than or equal tothis limit is to irrigate the ablation electrode with saline to provideconvective cooling so as to control the electrode-tissue interfacetemperature and thereby prevent an increase in impedance. Accordingly,irrigation of braided conductive member 28 and the tissue site at whicha lesion is to be created can be provided in the present invention. FIG.9 illustrates the use of an irrigation manifold within braidedconductive member 28. An irrigation manifold 100 is disposed along shaft12 inside braided conductive member 28. Irrigation manifold 100 may beone or more polyimide tubes. Within braided conductive member 28, theirrigation manifold splits into a number of smaller tubes 102 that arewoven into braided conductive member 28 along a respective filament 34.A series of holes 104 may be provided in each of the tubes 102. Theseholes can be oriented in any number of ways to target a specific site orportion of braided conductive member 28 for irrigation. Irrigationmanifold 100 runs through catheter shaft 12 and may be connected to anirrigation delivery device outside the patient used to inject anirrigation fluid, such as saline, for example, such as during anablation procedure.

The irrigation system can also be used to deliver a contrast fluid forverifying location or changes in vessel diameter. For example, acontrast medium may be perfused prior to ablation and then after anablation procedure to verify that there have been no changes in theblood vessel diameter. The contrast medium can also be used duringmapping procedures to verify placement of braided conductive member 28.In either ablation or mapping procedures, antithrombogenic fluids, suchas heparin can also be perfused to reduce thrombogenicity.

FIG. 10 illustrates another way of providing perfusion/irrigation incatheter 10. As illustrated in FIG. 10, the filaments 34 that comprisebraided conductive member 28 may be composed of a composite wire 110.The composite wire 110 includes a lumen 114 containing an electricallyconductive wire 112 that is used for delivering ablation energy in anablation procedure or for detecting electrical activity during a mappingprocedure. Composite wire 110 also contains a perfusion lumen 116.Perfusion lumen 116 is used to deliver irrigation fluid or a contrastfluid as described in connection with FIG. 9. Once braided conductivemember 28 has been constructed with composite wire 110, the insulation118 surrounding wire filament 112 can be stripped away to form anelectrode surface. Holes can then be provided in perfusion lumen 116 tothen allow perfusion at targeted sites along the electrode surface. Aswith the embodiment illustrated in FIG. 9, the perfusion lumens can beconnected together to form a manifold which manifold can then beconnected to, for example, perfusion tube 120 and connected to a fluiddelivery device.

Methods of Use

Reference is now made to FIG. 11 which illustrates how a catheteraccording to certain embodiments of the present invention may be used inendocardial applications.

In an endocardial procedure, shaft portion 12 is introduced into apatient's heart 150. Appropriate imaging guidance (direct visualassessment, camera port, fluoroscopy, echocardiographic, magneticresonance, etc.) can be used. FIG. 11 in particular illustrates shaftportion 12 being placed in the left atrium of the patient's heart. Onceshaft portion 12 reaches the patient's left atrium, sheath 33 may beretracted and braided conductive member 28 may be inverted to itsdeployed state, where, in the illustrated embodiment, braided conductivemember 28 forms a cone-type shape including a distally-facing,ring-shaped surface. External pressure may be applied along shaftportion 12 to achieve the desired level of contact between braidedconductive member 28 and the cardiac tissue. In one embodiment, mappingof electrical impulses may be achieved with braided conductive member28. In another embodiment, energy is applied to the cardiac tissue incontact with braided conductive member 28 to create an annular lesion.The energy used may be RF (radiofrequency), DC, microwave, ultrasonic,cryothermal, optical, etc.

In some embodiments, the braided conductive member may be configuredsuch that it forms a distally-facing, ring-shaped surface before thebraided conductive member is introduced to the heart.

Braided conductive member 28 may be used for mapping and/or ablation inother chambers of the heart. FIG. 13 shows catheter 10 with braidedconductive member 28 used in a method of treating ventriculartachycardia. In this illustrated embodiment, the tachycardia isemanating from the outflow track 1320 of ventricle 1300, which mayrepresent either a right or left ventricle. In the illustrated method,the braided conductive member 28 is placed in a partially invertedposition such as illustrated in FIG. 4. The partially invertedconfiguration leaves a distal end 18 extending beyond a distally facingsurface 1310. In this embodiment, distal end 18 extends partially intothe outflow track 1320 and may aid in positioning braided conductivemember 28 relative to outflow tract 1320.

Distal end 18 forms a proboscis that may be used in cannulating a bloodvessel such as outflow tract 1320. Where desired, catheter 10 may beformed with an extension forming a longer proboscis that may extendfurther into a blood vessel such as outflow tract 1320. The proboscismay, for example, be long enough to extend beyond pulmonary valve 1322.Providing a catheter with a longer proboscis may aid in positioningbraided conductive member 28 relative to the ostium 1324 of outflowtrack 1320. Positioning provided by a proboscis may aid in assuring astable contact between surface 1310 and the endocardium so that reliablemapping and ablation may be achieved.

FIG. 12 shows an enlarged view of a portion of surface 1310. In thisexample, surface 1310 is defined by filaments 34 of braided conductivemember 28. Braided conductive member 28 serves as a substrate forholding multiple electrically active sites 50. In the illustratedembodiment, electrically active sites are formed by selectively removinginsulation from filaments 34. The insulation may be removed in anysuitable manner, such as by milling or laser ablation techniques.

In the illustrated embodiments, the electrically active sites 50 faceoutwards from the center of braided conductive member 28. As thesurfaces of braided conductive member 28 comes in contact with tissue,one or more of the electrically active sites will be in electricalconnection with that tissue. Impedance measurement techniques as knownin the art may be used to detect which electrically active sites makecontact with tissue.

Because filaments 34 are electrically conducting, a conducting pathbetween the electrically active sites 50 and controller 8 is formedthrough cable 6. Controller 8 may therefore send or receive signals tothe electrically active sites 50. In some embodiments, conductivefilaments are electrically insulated except where electrically activesites 50 are formed. In this way, electrically active sites on separateones of the filaments 34 may be separately accessed by controller 8. Inother embodiments, one or more of the filaments 34 may be in electricalcontact with each other. In this embodiment, exposed regions on multiplefilaments may collectively form an electrically active site.

Separate access to the electrically active sites 50 allows controller 8to configure braided conductive mesh 28 to send or receive electricalsignals in a configurable pattern by selecting specific ones of theelectrically active sites 50 to access simultaneously. For example, thesurface 1310 illustrated in FIG. 13 may be divided into quadrantssurrounding ostium 1324. The electrically active sites in each quadrantmay be separately accessed for mapping purposes to determine whichquadrant contains the focus of a tachycardia. Access sites in quadrantsis just one example of a configuration that may be used. Controller 8may access the electrically active sites 50 in any combination or mayaccess electrically active sites individually. In this way, a focus of atachycardia may be detected with very high resolution. In oneembodiment, thirty-six electrically active sites are disposed on braidedconductive member 28. However, any number of electrically active sitesmay be used.

Providing a stable substrate for the electrically active sites furtherincreases the resolution with which sites for mapping or ablation areselected. Braided conductive member 28 is desirable for use in mappingand ablation procedures because it provides a substrate that holds theelectrically active sites in a stable fashion during a mapping orablation procedure.

In use, catheter 10 may be positioned near the suspected focus of atachycardia. It may be stably positioned, such as by cannulating a bloodvessel with a proboscis extending from catheter 10 or by pressing asurface 1310 against a wall of the heart. Braided conductive member 28may be configured as desired such as in an inverted or partiallyinverted configuration as described above. Once positioned, controller 8may receive signals through conductive filaments 34 from selectedelectrically active sites 50 for passive mapping. Alternatively,controller 8 may send stimulus signals through the conductive filaments34 to selected ones of the electrically active sites 50 for pace mappingin connection with a surface ECG, as is know in the art. If a focus onthe tachycardia is detected, controller 8 may send RF signals throughthe conductive filaments 34 to selected ones of the electrically activesites 50 for ablation. In this way, a single catheter may be used forpassive mapping, pace mapping and/or ablation.

Controller 8 may send RF energy for ablation to all of the electricallyactive sites 50 on surface 1310, thereby providing ablation energysubstantially around the parameter of ostium 1324. When operated in thisconfiguration, ablation may cause an annular lesion. However, where anannular lesion is not required to either ablate the focus or blockre-entry circuits, the ablation energy may be provided to groups ofelectrically active sites to create different ablation patterns. Forexample, ablation energy may be provided to a single electrically activesite 50 or a small number of electrically active sites in closeproximity to ablate tissue at one point. Alternatively, a group ofelectrically active sites positioned in a line or arc on surface 1310may be formed. When ablation energy is applied to this group, a lesionin the shape of a line or arc may be formed.

FIGS. 14A, 14B, and 14C illustrate use of braided conductive member 28in an alternative process for detecting and treating arrhythmias. Inthis embodiment, braided conductive member 28 has been introduced into achamber of a heart, such as a ventricle 1300. In this embodiment,braided conductive member 28 has been configured as shown in FIG. 5 toprovide a relatively planar surface without a distal end 18 forming aproboscis as illustrated in FIG. 13. Surface 1310 may therefore bepressed against the wall of a chamber of the heart. Braided conductivemember 28 is flexible and may therefore conform to the shape of thesurface, creating good electrical and mechanical contact between theelectrically active sites 50 and the surface of the heart. The positionfor contacting braided conductive matter 28 to the heart may be selectedbased on a suspected location of a focus of an arrhythmia. Asillustrated by FIG. 14A, the selected site need not be limited byplacement relative to outflow tract 1320 or other blood vessel.

Once braided conductive member 28 is positioned, controller 8 may sendand/or receive signals from the electrically active sites for mappingand/or ablation. It is not necessary, however, that braided conductivemember 28 be used for both mapping and ablation. It may, for example, bedesirable to use an ablation catheter of a different shape for ablatingtissue once foci of an arrhythmia are identified. To facilitate use ofmultiple catheters, a navigation system 1410 as is known in the art maybe employed in connection with a mapping and/or ablation process. Anavigation system may create a set of transverse electric or magneticfields with a gradient. A sensor positioned within the electric ormagnetic fields that is sensitive to the strength of the field in eachof the transverse directions may be used to identify the position of acatheter. Such a navigation system would allow, for example, braidedconductive mesh 28 to be used for mapping of cardiac arrhythmia. Once afocus of the arrhythmia is detected, the position of the focus may berelated to positions as determined by the navigation system. Anadditional catheter may be inserted for ablation at the desired locationas indicated by the navigation system, with or without removing braidedconductive member 28.

However, the braided conductive mesh may be used for ablation and may beconfigured to provide a wide range of ablation patterns. FIG. 14B showsthe surface of ventricle 1300 as seen in the direction indicated by theline B-B in FIG. 14A. FIG. 14B illustrates an ablation pattern that maybe created by repositioning catheter 10, and therefore braidedconductive member 28, and then applying ablation energy with braidedconductive member 28 in different positions. For example, lesions 1450A,1450B, and 1450C are substantially annular lesions. Such lesions may beformed by providing ablation energy to all of the electrically activesites on surface 1310. Each of the successive lesions may be formed bymoving catheter 10 in the direction M between each application ofablation energy.

In the example of FIG. 14B, lesion 1450D is also formed by movingcatheter 10 in the direction M. In this example, lesion 1450D is alsoannular, but with a radius smaller than lesions 1450A, 1450B, and 1450C.A smaller lesion may be formed by manipulating braided conductive member28 to present a smaller surface area 1310 against the wall of the heart.The surface area may be changed, for example, by manipulation of cable22 as described above.

FIG. 14B also illustrates another type of flexibility provided bybraided conductive member 28. Lesion 1450E is shown to be in the shapeof a line or segment. Such a lesion may be formed by providing ablationenergy to only a subset of the electrically active sites on surface1310. As demonstrated by FIG. 14B, the shape and size of a lesion formedby ablation using braided conductive member 28 may be controlled usingmultiple parameters including the position of catheter 10, the shape ofbraided conductive member 28 and the pattern of electrically activesites used in driving ablation energy.

FIG. 14C illustrates a further example of an ablation pattern that maybe formed. Catheter 10 may be moved in any desired direction toreposition braided conductive member 28. In the example shown in FIG.14C, catheter 10 has been moved in a circular pattern to create acircular pattern of overlapping annular lesions 1460A, 1460B, 1460C,1406D, 1460E, and 1460F. Other lesion patterns are possible. Forexample, multiple annular lesions may be overlapped in a pattern similarto the olympic rings as shown in FIG. 14D. In FIG. 14D lesions 1470A,1470B, 1470C, 1470D, and 1470E are formed by successive applications ofablation energy with braided conductive member 28 in differentpositions.

The examples of FIGS. 14B, 14C, and 14D illustrate the flexibility ofpatterning lesions formed by ablation with braided conductive member 28.This flexibility makes such a catheter suitable for detecting andtreating arrhythmias, such as those occurring in the ventricles. Thebraided conductive member may be fully deployed to create a relativelylarge surface, such as 1310, for mapping. For example, surface 1310 mayhave a diameter in excess of 15 mm and in some embodiments has adiameter of between about 25 and 30 mm. Mapping over such a large andstable area increases the success rate for accurately localizing foci.Also, mapping over such a wide area can speed up the entire procedure,reducing stress on patient. Ablation energy may also be provided inconfigurable patterns across this relatively large surface.

Furthermore, the fact that braided conductive member 38 does not createa continuous surface can provide benefits in cooling during an ablationprocedure. Cooling may be provided by the natural flow of blood in theheart or may be enhanced through irrigation as described above.Providing cooling allows for higher energies or longer ablation times,therefore making the braided conductive member 28 well suited forablating arrhythmic foci in the ventricles, which tend to be relativelydeep foci. Such a design may be particularly advantageous for treatingventricular tachycardia, particularly those with foci in the region ofthe ventricular outflow tract where it has traditionally be difficult tostably position a mapping catheter for accurate localization of foci andwhere it has also been traditionally difficult to ablate a broad anddeep region necessary to destroy the foci or block re-entry. Such adesign also may be particularly advantageous in treating idiopathicventricular tachycardia that has been traditionally difficult to treat.

However, the method and apparatus described herein are not limited foruse in connection with detection and treatment of ventriculartachycardia.

Having thus described several aspects of at least one embodiment of thisinvention, it is to be appreciated that various alterations,modifications, and improvements will readily occur to those skilled inthe art. Such alterations, modifications, and improvements are intendedto be part of this disclosure, and are intended to be within the spiritand scope of the invention. Accordingly, the foregoing description anddrawings are by way of example only.

What is claimed is:
 1. A method of treating an arrhythmia in a heart,comprising the acts of: (a) introducing a substrate into a chamber ofthe heart; (b) placing the substrate in contact with the heart while ina first configuration; (c) performing at least one of mapping and pacingby transmitting electrical signals between the substrate and a controllocation; (d) reconfiguring the substrate into a second configuration,different than the first configuration; (e) forming a first annularlesion that encircles a first region by ablating a region of the heartadjacent the substrate; (f) repositioning the substrate; and (g) forminga second annular lesion that encircles at least a portion of the firstregion encircled by the first annular lesion.
 2. The method of claim 1,additionally comprising the acts of: (h) repositioning the substrate;(i) forming a third annular lesion at least partially overlapping thefirst annular lesion and the second annular lesion.
 3. The method ofclaim 2, wherein less than half of area within the third annular lesionis common to each of the first and second annular lesions.
 4. The methodof claim 1, wherein the act (a) comprises introducing a braidedconductive member into a chamber of the heart.
 5. The method of claim 1,wherein the act (d) comprises reconfiguring the substrate into a secondconfiguration, having a smaller surface area than the firstconfiguration.
 6. The method of claim 5 wherein: the act (a) comprisesintroducing a braided conductive member in a chamber of the heart; andthe act (d) comprises changing a spacing between a proximal end and adistal end of the braided conductive member.
 7. The method of claim 1,wherein: the substrate while in the first configuration contacts theheart over a first area; and the act (e) comprises ablating a region ofthe heart adjacent the substrate that is smaller than the first area. 8.The method of claim 7, wherein: the substrate comprises a braidedconductive member having a plurality of electrically active sites; andthe act (e) comprises providing ablation energy to a subset of theplurality of electrically active sites.
 9. The method of claim 1,wherein the act (d) of reconfiguring comprises moving the center of thesubstrate away from the heart.
 10. The method of claim 1, wherein thesubstrate has a proboscis extending therefrom and the act (b) comprisescannulating a blood vessel connected to the heart with the proboscis.11. The method of claim 1, wherein: the arrhythmia is an idiopathicventricular tachycardia; the chamber of the heart is a ventricle; andthe act (e) additionally comprises passing a fluid through thesubstrate.
 12. The method of claim 1, wherein less than half of areawithin the second annular lesion is common to the first annular lesion.13. The method of claim 1, wherein the first and second annular lesionsrespectively encircle first and second regions of a heart wall, andwherein neither of the first and second regions of the heart wallcomprises an ostium of a blood vessel.
 14. A method of using a cathetercomprising a substrate, comprising the acts of: (a) introducing thesubstrate into a ventricle of the heart, the substrate comprising adistal end; (b) configuring the substrate in a first configurationwherein the distal end of the substrate forms a proboscis extending fromthe substrate; (c) with the substrate in the first configuration and theproboscis cannulating a blood vessel connected to the heart, ablating afirst lesion on a wall of the ventricle, the first lesion at leastpartially encircling a first region of the wall that includes an ostiumof the blood vessel; (d) configuring the substrate in a secondconfiguration wherein the substrate is inverted such that an annularsurface of the substrate extends beyond the distal end; (e) with thesubstrate in the second configuration, ablating a second lesion on thewall of the ventricle, the second lesion encircling a second region ofthe wall that does not include any blood vessel ostia.
 15. The method ofclaim 14, wherein the first lesion fully encircles the first region.